In tyre manufacturing, adhesive mixes, commonly known as cements, are organic-solvent-based. Adhesive mixes of this sort are highly adhesive and easy to use, mainly on account of rubber dissolving readily in organic solvents and so blending with other rubber to form practically one piece once the organic solvent evaporates.
This type of adhesive mix has the major drawback of containing a large amount of organic solvent, which, as is known, is highly volatile and, because of its characteristics, may pose environmental problems.
For all these reasons, recent European directives have imposed a drastic reduction in the use of organic solvents in tyre manufacturing, thus forcing manufacturers to devise alternative solutions to ensure correct adhesion of rubber layers.
One alternative to conventional adhesive mixes is water-base adhesive mixes, in which organic solvent is replaced by water solvent, and which pose the problem of ensuring dispersion in water of intrinsically hydrophobic ingredients. This is done using emulsifiers which, as is known, comprise a hydrophobic group capable of bonding the ingredient in question, and a hydrophilic group capable of ensuring its dispersion in water. Tests show, however, that the presence of emulsifiers may impair the adhesive strength of the adhesive mix.
Minimizing the amount of emulsifiers used in water-base adhesive mixes is therefore a crucial issue.
One of the components requiring most emulsifier is carbon black, both on account of the organic nature of commonly used carbon black, and the large amount of it used in the adhesive mix.